Sullaih's foreskin will be sliced off without anaesthetic, with the cheering crowd goading him on.

He must endure the pain without tearing, wincing, flinching or falling. To be a Mumasaaba man is to show no weakness.

"My heart is racing," his mother Salima Nesiho says of her first born.

Hundreds of Bamasaaba males between 16 and their early 20s are being initiated into manhood this rainy season, in a time-honoured ceremony called Imbalu, held every second year.

The season begins with a festival of traditional dancing, millet beer, roasted meat and offerings to ancestors.

The candidates and members of their families are smeared in millet paste to protect them from bad spirits.

Each is then paraded from village to village singing, dancing and visiting relatives over three days.

"It is a way of helping this young man to speak in public introducing the gentleman into public life," says James Kangala, a Bamasaaba man and founder of a cultural council based at the nearby town, Mbale.

The ceremony can be traced through records dating back 200 years, though the Bamasaaba believe the ritual predates these by several hundred years, with its origins lost in time.

There have been few concessions to modernity, though fresh blades are now used to prevent the spread of HIV.

Traditional surgeons or bashebi are believed to be appointed by spirits of ancestors to perform the circumcisions.

Robert Nangoye has circumcised hundreds of males over his 15 years in the role.

For a Mumasaba boy to be called a man, you have to pay a debt to the culture. It's our law, he says.

Males who try to escape it are hunted down and circumcised by force.

They'll capture you, even if you go to Europe and back. As long as he's from Bamasaaba, he will have to be circumcised, Mr Nangoye says.

However not all Bamasaaba support the ritual.

Lenard Massa, who was circumcised the traditional way in 1988, says males should have a choice.

If you go through the cultural way they take you through a painful exercise, Mr Massa says.

His young son was circumcised in a hospital, though it means he won't ever be recognised as a Bamasaaba man.

I didn't want him to go through what I did, Mr Massa says.

But for most of the tribe, the ceremony remains deeply significant. They have always been open to outsiders witnessing Imbalu, and are beginning to open up to tourists.

I found the ceremonies fascinating, says Floris Burgers, 22, from the Netherlands, who saw them this season while working in the area.

I can imagine some foreigners might find them a bit scary, but if you know the story behind the practice, there is not much to be afraid of.

The tourist board has begun promoting the opening and closing festivals, along with better known local attractions such as coffee plantations, the waterfalls and hiking at Mount Elgon.

Thousands turned out for the opening festival this year, mostly from surrounding regions.

The Government now hopes to attract international visitors.

It's something that is very young, says Stephen Asiimwe, head of the Uganda Tourism Board.

Attendance fees are being considered to help build a cultural centre celebrating and preserving the tribe's history.

It is a recognition of the importance of this Imbalu for our tribe, Mr Kangala says.

Imbalu culminates on the third day when the male is finally circumcised. If he does not flinch, he's rewarded with money, a phone, livestock and other gifts.

If you are able to face the knife and bear that pain with bravery, you are now ready to face any other situation in life, Mr Kangala says.

For 19-year-old Sullaih and his family, a lot hinges on a successful circumcision.

Any sign of weakness or reluctance could mean he is forcibly circumcised or called a coward for the rest of his life.

As a symbol of family unity and an offering to the spirits of ancestors, a goat's heart and lungs are pitched on a stick over the spot where Sullaih will become a man.

The smell of millet beer is thick in the circle surrounding the 19-year-old as the surgeon readies his blade.

The crowd erupts as he begins to cut. He stands firm, his face unmoving. It is over in seconds.

After hours on his feet, Sullaih is at last allowed to sit at the centre of the crowd.